DC Step-up (Boost) Voltage Regulator

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Old 05-23-08, 08:56 AM
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DC Step-up (Boost) Voltage Regulator

Hi all,

I am trying to regulator my boat's house battery bank's variable input voltage (10.8-14.6V) to a constant 13.8V. I'd like the regulator to be able to supply 5-10A of current.

I have searched quite a bit on the net and can only find products that have standard voltages of 12, 15, 18, etc. There are things that can be adjusted to 13.8V, but not with the amperage I need.

Please offer any suggestions!

Thanks for your help,
Aaron Norlund
 
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Old 05-23-08, 09:21 AM
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What is the purpose of doing this? Knowing the reason may help us determine an effective solution.
 
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Old 05-23-08, 10:05 AM
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Pooks,

I am trying to provide a constant 13.8V to cold cathode lamps:

Logisys CCFLs

I made snazzy little boxes to put these in for interior cabin lights in my boat. Everything was great, but I did all of the testing using a stable 13.8V power supply. In the boat, even with a fully charged 12.62V bank, the lights have trouble starting up.

I've put a lot of time into these damned things, so I got to thinking and realized all of these lights are designed to be used with a computer's stable 13.8V DC output. So it follows that if I can step-up the voltage going to these light's transformers, they should work fine.

You can see my little lights here:
CCFL Cabin Lights

Scroll in the picture series and you'll see them.

Thank you for your help!
Aaron N.
 
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Old 05-23-08, 11:32 AM
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I see some options

Originally Posted by blahman View Post
In the boat, even with a fully charged 12.62V bank, the lights have trouble starting up.
My first thought is to pitch the existing supplies and get those that work. Lots of supplies out there targeting car neon lights, etc. Any decent auto/marine design needs to work at 11 volts.

Plan B, like you say, is to keep them and boost the input voltage. I did a design once that boosted 12v to 14v, regulated, used as a SLA battery charger. Maxim is someone I'd look to for a IC, and note a couple of things. You will need to find/make an inductor, work some equations, but there is maybe just 10 or so parts in a DC boost design. Note that these WILL emit some RF, so in a boat, you need to make sure that you won't get a signal in the VHF band, etc. If you use LORAN, that's likely worst case. I would tend not to want to do a single, large converter. I don't know of a commercial 10 amp boost convertor, but there could be one.
Are all lights on at the same time? How many lights total?
 
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Old 05-23-08, 12:15 PM
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Telecom,

Thank you for the reply. There are six lights on the circuit, each with the potential of drawing .6 amps. They are switched on individually; it would be rare for all to be on at the same time. Should never go above 3.2 amps even with all running, so 5 amps from a converter is adequate.

The problem with purchasing pre-made marine lighting is the cost; to get low-consumption lighting of the luminosity I want is would be well over $1200. I've purchased and fabricated all 13 lights for under $150. So another $100 in regulators, plus ten hours of solder time would be a good compromise.

Thanks for your help,
Aaron N.
 
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Old 05-23-08, 05:18 PM
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Have you thought about using an AC inverter and a 120-volt computer power supply?

You'd essentially be building the same thing to step up the DC voltage. Basically you have to convert it to AC, step it up, convert it back to DC, regulate it, and filter it.
 
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Old 07-07-08, 04:26 PM
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This is a common enough thing for the ham radio folks who are always fighting against the loss of RF power with lower battery voltages. One standard solution is the MFJ-4416 Battery Booster. $139, but it's a canned solution and will do more than you need.

http://www.mfjenterprises.com/Produc...uctid=MFJ-4416


There's also this from Leo Lehner (W4RRY), a lot of ham operators are engineers, so it isn't unusual to see they selling gear that beats the professionals. $120 but a lot more current. If you are also running a VHF radio and would like it to work to spec you might consider this.

http://members.cox.net/w4rry/index.html
 
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Old 07-07-08, 07:29 PM
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Small DC motor hooked to small AC gen and then rectify the output?
But, you'd still need a regulator or governor of sorts, and it would make some noise.
 
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Old 07-07-08, 07:42 PM
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Maybe. . .

Nicads that are charged in parallel or series-parallel and discharged in series through your load,
this charge/discharge function being done by a slow-moving electromechanical switch or relays driven in sequence.

The voltage across the load would vary slightly as the batteries are switched in and out.
 
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Old 07-08-08, 10:06 AM
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TG Electronics do them too, and will supply up to 15v, they even have a marine version which might solve some problems you don't have yet.

http://stores.tgelectronics.org/StoreFront.bok
 
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